Conveyor belts that have the feed portion of the belt located inside a pipe are described in U.S. Pat. No. 5,052,545, in the applicant's earlier South African patent 2002/00644 and in U.S. Pat. Nos. 5,735,386, 6,405,855, 6,422,381 and 6,675,958.
The applicant's patent 2002/00644 dealt primarily with diamond recovery where the conveyor belt feed being located inside a pipe improved security by enclosing the diamond-bearing gravel, with its return portion located below, as in the above cited US patents. The pipe has a hinge at an intermediate position of its length, capable of hinging the pipe into a reduced length, for transport to remote sites, with the belt still in the pipe. Idler rollers are provided at intervals to support the belt on its return stretch. The drive roller, return idler and idler roller supports are mounted on the pipe so that assembly of these items on site and set up is not required, so that maintenance is simplified. A key difficulty with this apparatus, however, is that a new belt cannot be installed in the pipe except by threading it through the pipe and then on site joining the ends to form a closed loop; a factory formed joint is not an available option. From practical experience of working in conditions where the material is damp or wet it adheres to the belt and causes spillage; this requires the belt to be scraped clean and belt scrapers do not function well with the type of belt joint that is possible on site, they become damaged or ineffectual and/or damage the belt at the joint.